Markus Hanke Posted June 19, 2016 Posted June 19, 2016 I am at a slight loss as to imagine , how that field is supported across vast reaches of space I should point out here that quantum fields are conceptually quite different from classical fields; they are not "supported" by anything, have no source, and do not actually describe the "state" of anything. They are simply a collection of operators attached to each event in spacetime, which may differ in phase from point to point - if you so will, they are a supporting structure which allows us to perform certain calculations at those events. The Standard Model contains at least 17 of those fields ( depending on how you count them ), all of which coexist at each event, and the excitations of which are precisely our elementary particles. As such, they cannot be considered a "medium" in any reasonable sense of the word.
Mike Smith Cosmos Posted June 19, 2016 Posted June 19, 2016 (edited) I should point out here that quantum fields are conceptually quite different from classical fields; they are not "supported" by anything, have no source, and do not actually describe the "state" of anything. They are simply a collection of operators attached to each event in spacetime, which may differ in phase from point to point - if you so will, they are a supporting structure which allows us to perform certain calculations at those events. The Standard Model contains at least 17 of those fields ( depending on how you count them ), all of which coexist at each event, and the excitations of which are precisely our elementary particles. As such, they cannot be considered a "medium" in any reasonable sense of the word.' supporting structure ' sounds a bit 'realy there ' . But do you mean , more of a mathmatical structure, for calculation purposes only ? Or am I putting words in your mouth? Then we are back to there not actually being anything there ? Nothing , just a passing EM wave . I suppose , I can't visualise a self contained . Curled up in a ball or somehow , it's unlike anything in our experience? Maths is a construct , but vaporous , not real . So what exactly is it describing , what is the ' thing ' down there that it is describing ? Mike Edited June 19, 2016 by Mike Smith Cosmos
ajb Posted June 19, 2016 Posted June 19, 2016 Mike, are you asking if these quantum fields are 'real'? I am not sure that has a great answer. We cannot directly observe these fields (these are operator valued distributions!), but we know how to work with them and produce phsyical observables. There is another approach to the subject of quantum field theory where we more-or-less forget about the fields and work directly with the algebra of observables. At least these algebras (really nets of) are obsevable things. However, this approach is very difficult to work with.
Mike Smith Cosmos Posted June 19, 2016 Posted June 19, 2016 (edited) " At least these algebras (really nets of) are obsevable things. However, this approach is very difficult to work with. " Ok . If they are observable things , tell me what you see ? What do they look like? Observe ? Tell me in words , or doodles , what you observe and see ? I am teetering on the border of insanity ! Please tell me what you see ? Mike Edited June 19, 2016 by Mike Smith Cosmos
ajb Posted June 19, 2016 Posted June 19, 2016 Tell me in words , or doodles , what you observe and see ? Okay, so for interacting phenomenologically reasonable theories, this algebraic approach has not been properly implimented. An observable is something you can (at least in principle) measure. In local algebraic quantum field theory, you start from an operator algebra (C*-algebra usually) and then take the self-adjoint operators to be the observables. You can then construct what you would actually measure in an experiment (once you have defined states and so on). But like I said, this does not yet work for the standard model.
Mike Smith Cosmos Posted June 19, 2016 Posted June 19, 2016 (edited) Okay, so for interacting phenomenologically reasonable theories, this algebraic approach has not been properly implimented.An observable is something you can (at least in principle) measure. In local algebraic quantum field theory, you start from an operator algebra (C*-algebra usually) and then take the self-adjoint operators to be the observables. You can then construct what you would actually measure in an experiment (once you have defined states and so on). But like I said, this does not yet work for the standard model.. A great scientist has recently said :- Science is in two distinct parts :physics and maths , , where the physics deals with the observation of reality and theories And the maths deals with the esoteric formulae which are exact but unreal . I probably have not quoted exactly but I will try and find the quote So the relevance ( if this quote is correct ) is : yes , if there is this beautiful maths that you have identified , then that is great and I will try to understand it. But I am after the REALITY of the PHYSICS which ( if this above quote is correct ) is the REALITY of what is there and going on . Mike Edited June 19, 2016 by Mike Smith Cosmos
ajb Posted June 19, 2016 Posted June 19, 2016 But I am after the REALITY of the PHYSICS which ( if this above quote is correct ) is the REALITY of what is there and going on . The reality is in comparing the (expectation) values of physical observables as predicted within a physical theory with observations/experiments. I am not sure if one can really get a deeper meaning of 'reality' in this context.
StringJunky Posted June 19, 2016 Posted June 19, 2016 The reality is in comparing the (expectation) values of physical observables as predicted within a physical theory with observations/experiments. I am not sure if one can really get a deeper meaning of 'reality' in this context. Reality is what is measured isn't it? Everything else is philosophy.
ajb Posted June 19, 2016 Posted June 19, 2016 Reality is what is measured isn't it? Everything else is philosophy. To my mind yes ... but others may disagree.
StringJunky Posted June 19, 2016 Posted June 19, 2016 (edited) To my mind yes ... but others may disagree. Most physical scientists wouldn't disagree would they. It makes sense to me anyway... finally! As a non-scientist it took me quite awhile what you and swansont et al were on about. But I realised once you you start getting fundamental the notion of what a thing 'is', in classical terms, evaporates to just parameters and the relationships between them; basically maths. Edited June 19, 2016 by StringJunky
ajb Posted June 19, 2016 Posted June 19, 2016 (edited) But I realised once you you start getting fundamental the notion of what a thing 'is', in classical terms, evaporates to just parameters and the relationships between them; basically maths. Indeed, so back to the opening post, I would avoid trying to define what space-time 'is', it is 'just' the mathematical space that consists of points that we can interpret as the potential locations and durations of physical events. Its local geometry we can interpret as describing gravity. Ripples in this local geometry are gravitational waves. The question of if space-time and its curvature are real is unanswerable. All we can say is that these mathematical ideas can be used to build theoreis that match well what we can observe. Edited June 19, 2016 by ajb 1
jerrygg38 Posted June 19, 2016 Posted June 19, 2016 There are two solutions to the gravitational wave problem. The Einsteinian solution is that a massive body such as a black hole interacts with space and time producing ripples which propagate through space.This solution specifies that space itself has properties. Thus if you got rid of all the mass in the universe you would still have space. The alternative solution is that space is nothing at all and filled with waves. Thus the the big bang the entire universe existed as a small ball of energy. Outside this ball was nothing at all. the expansion of the ball produced matter and photonic energy. The ripples we see are the radiated energy within that ball.
Strange Posted June 19, 2016 Posted June 19, 2016 There are two solutions to the gravitational wave problem. The Einsteinian solution is that a massive body such as a black hole interacts with space and time producing ripples which propagate through space.This solution specifies that space itself has properties. Thus if you got rid of all the mass in the universe you would still have space. The alternative solution is that space is nothing at all and filled with waves. Thus the the big bang the entire universe existed as a small ball of energy. Outside this ball was nothing at all. the expansion of the ball produced matter and photonic energy. The ripples we see are the radiated energy within that ball. One of those is a scientific theory. The other one sounds like something you made up.
Mike Smith Cosmos Posted June 19, 2016 Posted June 19, 2016 (edited) Indeed, so back to the opening post, I would avoid trying to define what space-time 'is', it is 'just' the mathematical space that consists of points that we can interpret as the potential locations and durations of physical events. Its local geometry we can interpret as describing gravity. Ripples in this local geometry are gravitational waves.The question of if space-time and its curvature are real is unanswerable. All we can say is that these mathematical ideas can be used to build theoreis that match well what we can observe.I think for something as vast and central to our universe as SPACE . We do need to define space well, if we are going to make theories and observations by the ' shed load' over the coming years . Do we not . Ok so we have some maths , but we need good sized portions of ' reality ' too, surely ? Mike Edited June 19, 2016 by Mike Smith Cosmos
StringJunky Posted June 19, 2016 Posted June 19, 2016 (edited) I think for something as vast and central to our universe as SPACE . We do need to define space well, if we are going to make theories and observations by the ' shed load' over the coming years . Do we not . Ok so we have some maths , but we need good sized portions of ' reality ' too, surely ? Mike Maths is the best way of describing reality that we have and it is unequivocal in its meaning to those that understand the language and want to communicate about it between themselves. The less ambiguity the better. Edited June 19, 2016 by StringJunky
Strange Posted June 19, 2016 Posted June 19, 2016 Ok so we have some maths , but we need good sized portions of ' reality ' too, surely ? The "reality" comes from comparing the maths against observation. What else can you do?
Mike Smith Cosmos Posted June 19, 2016 Posted June 19, 2016 The "reality" comes from comparing the maths against observation. What else can you do? Seems very ' Wooly ' at the moment. Nothing of very much substance. There are other unseen things like ' air ' and ' water ' which are similarly transparent , yet we can have a good scientific description, both maths and physics . But with Space it's all a bit of a mystery ? Wooly and vague . Mike .
Strange Posted June 20, 2016 Posted June 20, 2016 But with Space it's all a bit of a mystery ? Wooly and vague . It is a fantastically detailed and accurate model. We use it for everything from GPS satellites to detecting gravity waves from black holes billions of light years away. I suspect it is just your understanding that is "woolly".
MigL Posted June 20, 2016 Posted June 20, 2016 As StringJunky said, Mike, physicists build models, almost invariably mathematical models. These models then, allow them to make certain predictions about the behavior of the system being modeled. These predictions are then tested against experimental evidence and observation, to judge the validity of the model. Sometimes the model is valid ( agrees with observation/experiment ) under certain circumstances, but leads to inconsistencies in others. A perfect example is GR's indication of a singularity of infinite density central to a Black Hole. This anomaly indicates that GR is invalid under those circumstances, and points to the need for Quantum Gravity. The gas laws, and Hydrodynamics, that we have as models allow us to predict the behavior of air and water under most circumstances, but they also need modification under certain conditions ( compressible vs. incompressible flows ) or they are invalid. 1
Mike Smith Cosmos Posted June 20, 2016 Posted June 20, 2016 (edited) It is a fantastically detailed and accurate model. We use it for everything from GPS satellites to detecting gravity waves from black holes billions of light years away. I suspect it is just your understanding that is "woolly"..Well I can concede my understanding is woolly about space . I just wish I could get over this ' bit , that space is absolutely empty, and that electro magnetic waves do not need a medium ( however thin ' ) to function in. Even if the medium was 'very very very thin ' , then I could come to terms with it , in my head . But my head will not let me concede that there is not ' something more than absolutely nothing ' it does not have to be matter , it can be an influential ' field ' , ( the sum total of the rest of the universe 'field', but some form of field , not NOTHING ) , surely ? Somebody , tell me there IS something there ( even if we do not understand it ) , however thin? Mike Edited June 20, 2016 by Mike Smith Cosmos
StringJunky Posted June 20, 2016 Posted June 20, 2016 (edited) Well I can concede my understanding is woolly about space . I just wish I could get over this ' bit , that space is absolutely empty, and that electro magnetic waves do not need a medium ( however thin ' ) to function in. Even if the medium was 'very very very thin ' , then I could come to terms with it , in my head . But my head will not let me concede that there is not ' something more than absolutely nothing ' Somebody , tell me there IS something there ( even if we do not understand it ) , however thin? Mike Rockets don't need a medium to move through,so, why should photons? The only difference is that photons generate their energy via reciprocating electrical and magnetic energy. Why can't they be extant from the vacuum of space like rockets? Edited June 20, 2016 by StringJunky
Mike Smith Cosmos Posted June 20, 2016 Posted June 20, 2016 (edited) Rockets don't need a medium to move through,so, why should photons? The only difference is that photons generate their energy via reciprocating electrical and magnetic energy. Why can't they be extant from the vacuum of space like rockets?Yes , but surely rockets DO need a medium otherwise they would just drop over the edge of the void , where space ran out , and there was absolutely nothing there , over the edge , nothing ! I thought Frank Willczek and Ed Whitton , had both come up with the ideas that there was something there , rather than nothing ? Perhaps it's this 'nothing' that I can not come to terms with ? Mike Edited June 20, 2016 by Mike Smith Cosmos
StringJunky Posted June 20, 2016 Posted June 20, 2016 Yes , but surely rockets DO need a medium otherwise they would just drop over the edge of the void , where space ran out , and there was absolutely nothing there , over the edge , nothing ! Perhaps it's this 'nothing' that I can not come to terms with ? Mike There is no edge to space.
Mike Smith Cosmos Posted June 20, 2016 Posted June 20, 2016 (edited) There is no edge to space..Well at least I can stop worrying about falling over the edge ! The bit I still struggle with is this lack of anything for electro and magno to sling shot with , other than each other or to work within ! Perhaps I have been brainwashed so much or too much , with capacitor plates and coil turns and metallic surfaces, up through my electronic days , in working with electro magnetism ? What about " I thought Frank Willczek and Ed Whitton , ( both Nobel Prize winners for their work ), had both come up with the ideas that there was something there , rather than nothing ? " I think ! Edited June 20, 2016 by Mike Smith Cosmos
MigL Posted June 20, 2016 Posted June 20, 2016 It used to be a common idea that a wave has to wave 'something', i.e. it needs a medium. However the model we use, relativity, doesn't require a medium. It also demands that there is no absolute reference frame. And since the medium would provide an absolute reference frame against which motion could be judged, a medium is not only not required, but actually forbidden. We'd have to get rid of relativity to make you happy, Mike. And, although we all like you, that's not gonna happen.
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